Floodplain Mapping

Our river corridor rich with life, critical to the health of our river and fishery. Mapping and development standards help to encourage healthy development and limit damages to property and risk to safety as a result of flooding.

Big Hole River Approximate Zone A Floodplain Mapping

The Big Hole River Approximate Zone A (also referred to as the “100 year floodplain” or “1% flood probability”) were completed spring 2013. The mapping covered 116 miles of Big Hole River from headwaters to mouth, except the portion within Silver Bow County which had been mapped previously.

Floodplain mapping provides legally defensible products with which counties can regulate development within the floodplain. Appropriate river floodplain development is critical to protect property, ensure health and safety of the public and responders during floods, maintain the long-term sustainability and health of our river floodplain, and provide protections for water quality, river side vegetation, and more.

– Intermediate Step: After state adoption, the state will submit the maps to FEMA for adoption. This process is expected to take several years to complete. The next steps are not dependent on this step.

Each county may adopt floodplain development standards that will provide guidance on appropriate floodplain development, such as river set-backs, structure height, etc. The Big Hole Watershed Committee drafted recommended language for new development standards to encourage incorporation of riparian health standards as well as standardize floodplain development across counties. A letter of support was sent to counties April 2015 to encourage floodplain map and development standard adoption:

View the Big Hole River Floodplain Maps

The BHWC Land Use Planning Committee & The Floodplain Mapping Team

The BHWC Land Use Planning Committee has led the effort to map the Big Hole River floodplain beginning in 2009. The Land Use Planning Committee is a sub-committee of the BHWC. During this project, this sub-committee was led by facilitator Jen Boyer of Future West. The committee is made up of county planners, state floodplain advisors, landowners and interest groups.

The Big Hole River Floodplain Maps were developed through partnerships: